Russia has expressed concern over U.S. plans to replace nuclear warheads with conventional charges on some intercontinental missiles, warning it would be impossible to tell one from the other on launch, the Financial Times said Friday.

A senior Kremlin official condemned the switch being discussed in the U.S. as “irresponsible”.

“You can imagine, a rocket is fired, especially from a submarine, and no one knows what kind of warhead it is carrying,” the official said. “It doesn’t say on the rocket whether it has a conventional or nuclear warhead.”

He said the Pentagon’s plans were “extremely dangerous” and the launch of such a missile could lead to an “inappropriate” response from other nuclear states.

The comments came a day after President Vladimir Putin referred to the danger, in his annual state of the nation address, although he made no specific reference to the U.S.
“The media and expert circles are already discussing plans to use intercontinental ballistic missiles to carry non-nuclear warheads. The launch of such a missile could . . . provoke a full-scale counter-attack using strategic nuclear forces,” said Putin.

The Russian president’s seventh state-of-the-nation address placed heavy emphasis on the need to modernize the country’s military forces, including its nuclear arsenal, to enable it to withstand external pressures.

Putin also said Russia needed to “preserve the strategic balance of forces”, noting that the U.S. was spending 25 times as much as Russia on defense. He pledged not to repeat the mistakes of the cold war, when the Soviet Union spent so much on arms that it weakened its economy, but warned that the arms race was not over — an apparent reference to U.S. plans to develop new types of nuclear weapons.

“What’s more, the arms race has entered a new spiral today with the achievement of new levels of technology that raise the danger of the emergence of a whole arsenal of so-called destabilizing weapons,” he added.

“There are still no clear guarantees that weapons, including nuclear weapons, will not be deployed in outer space. There is the potential threat of the creation and proliferation of small capacity nuclear charges.”

In February, the Pentagon unveiled its Quadrennial Defense Review — a major assessment of the capabilities needed by the U.S. over the next 25 years — which called for the conversion of some intercontinental ballistic missiles from nuclear warheads to conventional weapons.

While some military officers concede that problems exist regarding the difficulty for other countries to detect the kind of warhead launched, they say the changes are needed to improve U.S. strike capability.